Device and method for package warp compensation in an integrated heat spreader

ABSTRACT

A device and method for designing and manufacturing an integrated heat spreader so that the integrated heat spreader will have a flat surface on which to mount a heat sink after being assembled into a package and exposed to the heat of a die. This device and method for designing and manufacturing an integrated heat spreader would generate a heat spreader that would be built to compensate for deformations resulting from (1) physical manipulation during assembly, (2) thermal gradients during operation, and (3) differing rates of expansion and contraction of the package materials coupled with multiple package assembly steps at elevated temperatures so that one surface of the integrated heat spreader would have a flat shape.

FIELD

The invention relates to a device and method for package warpcompensation in an integrated heat spreader. More particularly, thepresent invention is a device and method that determines the warpage inan integrated heat spreader (IHS) and compensates for this warpage toimprove the heat dissipating properties of the IHS.

BACKGROUND

In the rapid development of computers many advancements have been seenin the areas of processor speed, throughput, communications, faulttolerance and size of individual components. Today's microprocessors,memory and other chips have become faster and smaller. However, with theincrease in speed, reduction in the size of components, and increaseddensity of circuitry found within a given chip/die, heat generation anddissipation have become a more critical factor than ever.

To facilitate the dissipation of the heat generated by a die, an IHS maybe affixed to the die and maybe used in conjunction with a heat sink.The IHS is affixed to the die with a layer of thermal interface materialthat is used to provide some adhesion between the IHS and the die andtransfer heat from the die to the IHS. In addition, a heat sink may beplaced on top of the IHS with a layer of a thermal interface materialplaced between the IHS and heat sink to facilitate a limited amount ofadhesion and transfer heat from the IHS to the heat sink. The heat sinkmay have vertical fans extending therefrom to increase the surface areaof the heat sink and facilitate the transfer of heat from the IHS to theambient air. As would be appreciated by one of ordinary skill in the artthese heat sinks may take many different forms and may include a smallelectric fan.

A package may be formed during the assembly process by affixing the dieto a substrate and then placing the IHS on top of the die and the heatsink on top of the IHS. The placement of the IHS on top of the die maybe accomplished utilizing an industrial robot arm with a grasping toolaffixed to the robot arm. The grasping tool may hold the IHS at theedges thereof and place it on top of the die.

Since the die may be made flat and rectangular or square in shape, theIHS is also designed to be flat so that the thermal interface materialbetween the die and the IHS and the thermal interface material betweenthe IHS and heat sink is of a uniform thickness to dissipate heatthroughout the die to the IHS and thereafter to the heat sink.

However, because the assembled package contains materials with differentcoefficients of thermal expansion, and because the package is assembledin steps at various temperatures and because temperature gradients existin a “powered-up” package the IHS will deform so that it no longerremains flat. Once this deformation occurs in the IHS, the thickness ofthe thermal interface material between the heat sink and the IHS wouldvary and the IHS would no longer be able to uniformly dissipate heatfrom the die to the heat sink.

Further, even though a die may be relatively small, the heat generatedby a die may not be evenly distributed throughout the die. In otherwords, hotspots may be seen in relatively small locations of a die wherepower consumption is high or heat generating circuits are present.

Therefore, what is needed is a device and method that can determine themanner in which an IHS will deform due to either or both physicalmanipulation of the IHS itself and heat fluctuations caused by poweringon and off the die in the package. Further, this device and methodshould compensate for the warpage seen in the IHS so that the distancebetween the IHS and heat sink remain approximately constant. Stillfurther, this device and method should compensate for hotspots on a dieand provide additional heat dissipating material in an IHS.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and a better understanding of the present invention willbecome apparent from the following detailed description of exemplaryembodiments and the claims when read in connection with the accompanyingdrawings, all forming a part of the disclosure of this invention. Whilethe foregoing and following written and illustrated disclosure focuseson disclosing example embodiments of the invention, it should be clearlyunderstood that the same is by way of illustration and example only andthe invention is not limited thereto. The spirit and scope of thepresent invention are limited only by the terms of the appended claims.

The following represents brief descriptions of the drawings, wherein:

FIG. 1 is an example of a package prior to assembly in an exampleembodiment of the present invention;

FIG. 2 is an example of an assembled package with the IHS 10 deformed bybowing out in the center due to differences in package materialcoefficients of thermal expansion or to physical manipulation and/ortemperature gradients in an example embodiment of the present invention;

FIG. 3 is an example of an assembled package with the IHS 10 havingdeformed by bowing in in the center due to differences in packagematerials coefficients of thermal expansion or to physical manipulationand/or temperature gradients in an example embodiment of the presentinvention;

FIG. 4A is an example of a Moiré Fringe image of a free-standing IHS 10as supplied by a manufacturer in an example embodiment of the presentinvention;

FIG. 4B is an example of a Moiré Fringe image of an IHS 10 at roomtemperature after being attached to the substrate in an exampleembodiment of the present invention;

FIG. 4C is an example of a Moiré Fringe image of an IHS 10 assembledinto a package, where the entire package is being soaked at 90 degreesCelsius in an example embodiment of the present invention;

FIG. 5A is an example of an IHS 10 having a shape designed to compensatefor the curvature seen in FIGS. 2, 4A, 4B and 4C in an exampleembodiment of the present invention;

FIG. 5B is an example of an IHS 10 having a shape designed to compensatefor the curvature seen in FIG. 3 in an example embodiment of the presentinvention;

FIG. 6 is an example of an assembled package in which the IHS 10 hasbeen processed utilizing the compensated IHS 10 shown in FIG. 5A or 5Band the logic shown in either FIG. 7 or FIG. 8 in an example embodimentof the present invention;

FIG. 7 is an example of an assembled package in which the IHS 10 hasbeen processed utilizing the compensated IHS 10 shown in FIG. 5A or 5Band the logic shown in either FIG. 7 or FIG. 8 taking into considerationa hotspot on die 50 in an example embodiment of the present invention;

FIG. 8 is an example of the process used to generate the IHS 10 shown inFIGS. 5A and 5B resulting in the IHS 10 shown in FIGS. 6 and 7 in anexample embodiment of the present invention; and

FIG. 9 is an example of the process used to generate the IHS 10 shown inFIGS. 5A and 5B resulting in the IHS 10 shown in FIGS. 6 and 7 in anexample embodiment of the present invention.

DETAILED DESCRIPTION

Before beginning a detailed description of the subject invention,mention of the following is in order. When appropriate, like referencenumerals and characters may be used to designate identical,corresponding or similar components in differing figure drawings.Further, in the detailed description to follow, exemplarysizes/models/values/ranges may be given, although the present inventionis not limited to the same. As a final note, well-known components ofcomputer networks may not be shown within the FIGs. for simplicity ofillustration and discussion, and so as not to obscure the invention.

FIG. 1 is an example of a package prior to assembly in an exampleembodiment of the present invention. FIG. 1 illustrates a package havinga die 50 attached to a substrate 30 using epoxy 60 with a finite amountof a thermal interface material (TIM) 20 placed on top of the die 50.This TIM 20 serves at least two primary purposes. First, it acts toconduct heat from the die to the integrated heat spreader (IHS) 10.Second, it also provides some adhesion between the IHS 10 and die 50.During the manufacturing process the IHS 10 is pressed down upon the TIM20 and adhesive 40. Thereafter, thermal interface material (TIM) 80would be placed on IHS 10 with the heat sink 70 placed on top of IHS 10.TIM 80 serves the same function as TIM 20 and may be composed of thesame material. Throughout the foregoing discussion the term package willrefer to the combination of, but not limited to, the substrate 30, epoxy60, die 50, thermal interface material 20, IHS 10, thermal interfacematerial 80, heat sink 70 and adhesive 40.

FIG. 2 is an example of an assembled package with the IHS 10 deformed bybowing out in the center due to physical manipulation and/or temperaturefluctuations in an example embodiment of the present invention. As shownin FIG. 2, the IHS 10 would absorb heat from die 50 through TIM 20 andbe held in place on the substrate 30 via adhesive 40. On top of the IHS10 a heat sink 70 or fan/heat sink combination (not shown) would bemounted to dissipate the heat absorbed by the IHS 10. However, since IHS10 and TIM 20 both experience significant stresses during the assemblyprocess and due to (1) physical manipulation and applied stresses duringpackage assembly and (2) thermal expansion and contraction when the dieis powered on and off, and (3) differences in material coefficients ofthermal expansion, the IHS 10 may change its shape. As indicated in FIG.2, the IHS 10 has bowed outward in the center so that TIM 80 is thickerin the center between heat sink 70 and IHS 10 as opposed to the outeredges. As previously discussed die 50 is connected to substrate 30 viaepoxy 60. IHS 10 is affixed to substrate 30 via adhesive 40. Further,die 50 is connected to IHS 10 via TIM 20.

FIG. 3 is an example of an assembled package with the IHS 10 havingdeformed by bowing in the center due to physical manipulation and/ortemperature fluctuations or differences in material coefficients ofthermal expansion in an example embodiment of the present invention. Thesole difference between FIG. 2 and FIG. 3 is the nature of thedeformation of the IHS 10. As would be appreciated by one of ordinaryskill in the art how the IHS 10 may be deformed is dependent on thematerials it is made of, the manner of handling, and the heat it isexposed to by die 50. Therefore, FIGS. 2 and 3 are provided merely asexamples of how an IHS 10 may deform. Regarding the heating of the IHS10 this is dependent upon how die 50 generates and dissipates heat. Forexample, die 50 may generate heat at a specific location such as thecenter of the die 50 or it may dissipate heat at the outer edges of thedie 50. The manner in which die 50 dissipates heat would directly affectthe deformation seen in the IHS 10. Since all other elements shown inFIG. 3 remain the same as that shown in FIG. 2, no further discussion ofthese elements will be provided here.

FIG. 4A is an example of a Moiré Fringe illustration of an IHS 10 assupplied by a manufacturer without being attached to a substrate 30 inan example embodiment of the present invention. It should be noted thatthe sensitivity of the Moiré Fringe illustration is 12.5 microns perfringe and that FIG. 4A is a top view of IHS 10. As indicated in FIG.4A, as received from the manufacturer the IHS 10 is effectively flat.

FIG. 4B is an example of a Moiré Fringe illustration of an IHS 10 afterbeing at room temperature as assembled into a package in an exampleembodiment of the present invention. As with FIG. 4A, it should be notedthat the sensitivity of the Moiré Fringe illustration is 12.5 micronsper fringe and that FIG. 4B is a top view of IHS 10. As indicated inFIG. 4B, after attachment to substrate 30 and at room temperature theIHS 10 significantly deformed as compared to that received from themanufacturer of the IHS 10. Since assembly occurs at room temperature,but curing of the sealant occurs at elevated temperatures, the entirepackage will warp when cooled to room temperature as seen in FIG. 4B.This can affect the adhesion between the heat sink 70 and the IHS 10using the thermal interface material 80, as shown in FIG. 2. Further, itwould affect the thickness of the thermal interface material 80 andthereby the heat dissipation capabilities of the heat sink 70. In FIG.4B a substrate is attached to the IHS, however, it is not visible in thepicture.

FIG. 4C is an example of a Moiré Fringe illustration of an IHS 10 in anassembled package, where the package is being exposed to a 90 degreeCelsius heat soak after attachment to substrate 30 (not shown) in anexample embodiment of the present invention. As previously mentionedregarding FIGS. 4A and 4B, it should be noted that the sensitivity ofthe Moiré Fringe illustration is 12.5 microns per fringe and that FIG. 4c is a top view of IHS 10. As indicated in FIG. 4C, as the temperatureof the entire package is increased to 90 degree Celsius, the IHS 10actually flattens slightly as compared to that shown in FIG. 4B that isat room temperature. However, there is still significant deformationinvolved in the IHS 10 shown in FIG. 4C to the point where two smallbumps are formed in the IHS 10.

FIGS. 4A through 4C are provided merely as examples of the type ofdeformation that may be seen in an IHS 10. As would be appreciated byone of ordinary skill in the art, the type of deformation that would beseen in the IHS 10 would depend upon the type of manipulation receivedduring assembly, the materials the IHS 10 and the other packagecomponents are composed of, the temperature range the IHS 10 is exposedto, etc. Therefore, in designing the IHS 10 to compensate for anydeformation seen it is necessary to provide a process and method thatcan handle any deformation possible. Further, as would be appreciated byone of ordinary skill in the art, a Moiré Fringe analysis is only onemethod of many for measuring deformation in the IHS 10. Other exampleswould include utilizing laser or even a touch probe to measure thedeformation. All these methods of measuring the shape of the IHS 10 willcollectively be referred to as a dimensional analysis from this pointforward.

FIG. 5A is an example of an IHS 10 having a shape to compensate for thecurvature seen in FIGS. 2, 4A, 4B and 4C in an example embodiment of thepresent invention. The convex shape of the IHS 10 illustrated in FIG. 5Ais depressed in the middle of the IHS 10. This convex shape would besupplied by the manufacturer of the IHS 10 and would compensate for thedeformation seen in FIG. 2 and FIGS. 4A through 4C. As would beappreciated by one of the ordinary skill in the art, the precisecurvature of the IHS 10 would depend upon the nature of the deformationseen.

FIG. 5B is an example of an IHS 10 having a shape to compensate for thecurvature seen in FIG. 3 in an example embodiment of the presentinvention. The IHS 10, shown in FIG. 5B, is provided by the manufacturerto compensate for the deformation seen in FIG. 3. In this case, thecenter of the IHS 10 is bowed outward. As would be appreciated by one ofthe ordinary skill in the art, the precise curvature of the IHS 10 woulddepend upon the nature of the deformation seen.

The IHS 10 illustrated in FIG. 5A and FIG. 5B are provided as merelyexamples of ways to compensate for deformations in an IHS 10. Dependingupon the deformation involved any number of different compensatingshapes may be provided. However, it should be noted that thecompensation provided in the IHS 10 should be opposite to that seen whenthe IHS 10 is mounted and is operating at the die temperature. The goalshould be for the compensated IHS 10 to be flat as will be discussedfurther in reference to FIG. 6.

FIG. 6 is an example of an assembled package in which the IHS 10 hasbeen processed utilizing the compensated IHS 10 shown in FIG. 5A or 5Band the logic shown in either FIG. 7 or FIG. 8 in an example embodimentof the present invention. It should be noted that the packageillustrated in FIG. 6 is identical to the packages shown in FIGS. 2 and3 with the exception that the IHS 10 is flat and the thermal interfacematerial 80 is of a constant thickness between the IHS 10 and the heatsink 70. Therefore, using the IHS 10 as shown in either FIG. 5A or FIG.5B it is possible once the IHS 10 is grasped by the robot tool andmounted onto die 50 and substrate 30 for it to take on a flat shape oncethe die 50 has obtained its operating temperature. The remainingelements shown in FIG. 6 remain unchanged from those previouslydiscussed in FIGS. 1 through 3 and will not be discussed further here.

FIG. 7 is an example of an assembled package in which the IHS 10 hasbeen processed utilizing the compensated IHS 10 shown in FIG. 5A or 5Band the logic shown in either FIG. 7 or FIG. 8 taking into considerationa hotspot on die 50 in an example embodiment of the present invention.The package shown in FIG. 7 is identical to that shown in FIG. 6 withthe exception that additional material 90 has been added to the IHS 10in order to facilitate the transmission of the heat from a specificlocation on die 50 to heat sink 70. This specific location on die 50 isreferred to as a hotspot since it generates more heat than otherportions over the die 50. As would be appreciated by one of ordinaryskill in the art, certain areas of the die 50 would generate more heatthan others due to the nature of the circuitry at that location. Byincreasing the thickness of the IHS 10 at that hotspot, it would bepossible to increase the heat transfer capacity of the IHS 10 at thatlocation since the distance between the IHS 10 and heat sink 70 would bereduced. Of course, the reverse is also possible and the IHS 10 may bemade thinner at selected points.

Before proceeding into a detailed discussion of the logic used by theembodiments of the present invention it should be mentioned that theflowcharts shown in FIGS. 8 and 9 may contain software, firmware,hardware, processes or operations that correspond, for example, to code,sections of code, instructions, commands, objects, hardware or the like,of a computer program that is embodied, for example, on a storage mediumsuch as floppy disk, CD Rom, EP Rom, RAM, hard disk, etc. Further, thecomputer program can be written in any language such as, but not limitedto, for example C++.

FIG. 8 is an example of the process used to generate the IHS 10 shown inFIGS. 5A and 5B resulting in the IHS 10 shown in FIG. 6 and 7 in anexample embodiment of the present invention. Processing begins inoperation 800 and immediately proceeds to operation 810. In operation810 a series of packages are built which include IHS 10 elements thatare flat in the as received condition from the supplier. Thereafter, inoperation 820 the packages are heat soaked or elevated to an approximatetemperature at which the die 50 is anticipated to operate at. Inoperation 830, a dimensional analysis is performed on the IHS 10 in eachpackage. This die dimensional analysis may use a Moiré Fringe analysisor some other technique for measuring the deformation in the IHS 10 ineach package. As part of the analysis performed in operation 830 astatistical analysis is performed on the results of the dimensionalanalysis received for each IHS 10. In this manner an average deformationfor each IHS 10 can be determined. Thereafter, processing proceeds tooperation 840 where a series of sets of IHS 10's are generated that havea slightly varying curvature to compensate for the warpage seen by thedie dimensional analysis performed in operation 830. Each set of IHS10's would comprise a statistically significant number of IHS 10's thatwould be of consistent shape with one another within a set, but wouldvary in degree of compensation from one set to another. In this mannerit would be possible to select the degree of compensation that bestcorrects the warpage seen. However, as would be appreciated by one ofordinary skill in the art, alternatively a simple series of IHS 10's maybe manufactured and installed in packages. This simple series of IHS10's may simply vary in the degree of compensation or curvature to forman equal distribution of IHS 10's of varying curvatures. In operation845 the IHS 10's are assembled into packages which comprise all theelements shown in FIGS. 1 through 3.

Still referring to FIG. 8, processing then proceeds to operation 850 inwhich the set of packages or package that has the flattest package whenpowered on is selected as the template for the IHS 10 design.Thereafter, in operation 860 it is determined if die 50 has any hotspotstherein. In the preferred embodiment operation 860 may be performed onthe assembled package with the heat sink 70 attached. In this way thecorrect stress and thermal conditions seen in actual use are achieved.In a preferred embodiment the hotspots are determined by temperaturesensors contained within the die 50 itself. In operation 870 for anyhotspots found in die 50, the curvature of the IHS is modified in thearea of the hotspot to eliminate it. Thereafter, processing proceeds tooperation 880 where the IHS 10 with the compensated shape for warpageand hotspots is manufactured. Processing then proceeds to operation 890where processing terminates.

FIG. 9 is an example of the process used to generate the IHS 10 shown inFIGS. 5A and 5B resulting in the IHS 10 shown in FIGS. 6 and 7 in anexample embodiment of the present invention. Processing begins executionin operation 900 and immediately proceeds to operation 910. In operation910, a finite element model is generated for the entire packageincluding the IHS 10. Finite element models comprise dividing astructure into a fixed number of smaller pieces or elements andinputting each element and its respective coordinates and relationshipsto other elements into a computer system. In addition, the properties ofeach element, such as, but not limited to, temperature expansioncoefficients, elasticity, heat transfer capability, modulus ofelasticity tensile strength, etc. are entered into the finite elementmodel. Processing then proceeds to operation 920 where the pressurepoints generated by the factory handling equipment, such as, but notlimited to, a robot arm and grasping device, are entered into the finiteelement model. These pressure points would comprise the amount ofpressure being placed on specific elements in the finite element model.The pressure experienced by these specific elements would be transferredto other elements contained within the model.

Still referring to FIG. 9, in operation 930 expansion coefficients andmechanical properties of each element of the package are also enteredinto the finite element model. In operation 940 the operatingtemperature of the die 50 is determined and which elements in the finiteelement model are affected by the temperature increase of the die 50.For example, the epoxy 60 would have a different expansion coefficientthan the IHS 10, or the heat sink 70. Processing then proceeds tooperation 950 where the hotspots, if any, in the die 50 are identifiedand the corresponding elements in the IHS 10 are also determined. Inoperation 960 a finite element model is executed and the warpage of theIHS 10 is determined from the finite element model. Thereafter, inoperation 970 the IHS 10 is redesigned to compensate for the warpageseen in operation 960. In operation 980 the finite element model isexecuted again with the exception that the IHS 10 compensated for thewarpage seen earlier is utilized in the model. This would entailreplacing the elements of the IHS 10 that are changed with new elementsof possibly different shape and existing in different positions.Thereafter, in operation 990 it is determined if any warpage can be seenutilizing the compensated IHS 10 in the finite element model. If thewarpage is not eliminated in the finite element model then processingreturns to operation 970 where it is repeated. However, if the warpageis eliminated in the finite element model in operation 980, thenprocessing proceeds from operation 990 to operation 1000. In operation1000 a series of sets of IHS 10's are generated that have a slightlyvarying curvature to the IHS 10 determined by the finite element model.Each set of IHS 10's would comprise a statistically significant numberof IHS 10's that would be of consistent shape with one another within aset, but would vary in degree of compensation from one set to another.In this manner it would be possible to select the degree of compensationthat best corrects the warpage actually seen as opposed to thatpredicted by the finite element model. As would be appreciated by one ofordinary skill in the art, no matter how well the finite element modelis generated it still may not behave precisely as predicted in actualoperation. Still further, as would be appreciated by one of ordinaryskill in the art, alternatively a simple series of IHS 10's may bemanufactured and installed in packages. This simple series of IHS 10'smay simply vary in the degree of compensation or curvature to form anequal distribution of IHS 10's of varying curvatures were the IHS 10generated by the finite element model being the medium IHS 10. Inoperation 1010 the IHS 10's are assembled into packages that compriseall the elements shown in FIGS. 1 through 3.

Still referring to FIG. 9, processing then proceeds to operation 1030 inwhich the set of packages or package that has the flattest package whenpowered on is selected as the template for the IHS 10 design.Thereafter, in operation 1040 it is determined if die 50 has anyhotspots therein. In the preferred embodiment operation 860 may beperformed on the assembled package with the heat sink 70 attached. Inthis way the correct stress and thermal conditions seen in actual useare achieved. In a preferred embodiment the hotspots are determined bytemperature sensors contained within the die 50 itself. In operation1050 for any hotspots found in die 50, the curvature of the IHS ismodified in the area of the hotspot to eliminate it. Thereafter,processing proceeds to operation 1060 where the IHS 10 with thecompensated shape for warpage and hotspots is manufactured. Processingthen proceeds to operation 1070 where processing terminates.

The benefits resulting from the present invention is that an IHS 10 maybe designed that will create an approximately flat package even aftermanipulation and exposure to fluctuations in temperature. With such anear flat package it is possible to effectively and uniformly dissipateheat from a die. In addition, it is possible to increase the heatdissipation capacity of the IHS 10 for specific locations associatedwith hotspots in a die 50.

While we have shown and described only a few examples herein, it isunderstood that numerous changes and modifications as known to thoseskilled in the art could be made to the example embodiment of thepresent invention. Therefore, we do not wish to be limited to thedetails shown and described herein, but intend to cover all such changesand modifications as are encompassed by the scope of the appendedclaims.

1. A method of manufacturing an integrated heat spreader, comprising:generating a finite element model of a package having a substrateconnected to a die connected to the integrated heat spreader connectedto a heat sink; executing the finite element model to generate theintegrated heat spreader with a shape having deformations; altering theshape of the integrated heat spreader to compensate for thedeformations; executing the finite element model using the integratedheat spreader having an altered shape to compensate for thedeformations; and repeating the altering of the shape of the integratedheat spreader to compensate for the deformations and execution of thefinite element model until no further deformations exist.
 2. The methodrecited in claim 1, wherein the generating a finite element model of apackage further comprises: dividing the substrate, the die, theintegrated heat spreader, and the heat sink into a plurality of elementshaving a certain spatial coordinate and connected to other elements ofthe plurality of elements.
 3. The method recited in claim 2, furthercomprising: associating properties with each of the elements of theplurality of elements, wherein the properties comprise mechanical andthermal properties, wherein thermal properties comprise coefficients ofthermal expansion.
 4. The method recited in claim 3, wherein thedeformations are due to the physical manipulation of the integrated heatspreader or heat absorption by the integrated heat spreader generated bythe die.
 5. The method recited in claim 4, further comprising:identifying hotspots on the die; determining associated elements on theintegrated heat spreader for the hotspots on the die; and modifying theheat spreader geometry to decrease local thermal resistance in theassociated elements on the integrated heat spreader.
 6. A computerprogram embodied on a computer readable medium and executable by acomputer for manufacturing an integrated heat spreader, comprising:generating a finite element model of a package having a substrateconnected to a die connected to the integrated heat spreader connectedto a heat sink; executing the finite element model to generate theintegrated heat spreader with a shape having deformations; altering theshape of the integrated heat spreader to compensate for thedeformations; executing the finite element model using the integratedheat spreader having an altered shape to compensate for thedeformations; and repeating the altering of the shape of the integratedheat spreader to compensate for the deformations and execution of thefinite element model until no further deformations exist.
 7. Thecomputer program recited in claim 6, wherein the generating a finiteelement model of a package further comprises: dividing the substrate,the die, the integrated heat spreader, and the heat sink into aplurality of elements having a certain spatial coordinate and connectedto other elements of the plurality of elements.
 8. The computer programrecited in claim 7, further comprising: associating properties with theeach of the elements of the plurality of elements, wherein theproperties comprise coefficients of thermal expansion.
 9. The computerprogram recited in claim 8, wherein the deformations are due to (a) thephysical manipulation of the integrated heat spreader (b) heatabsorption by the integrated heat spreader generated by the die (c) nonisothermal processing conditions for the package, coupled with differingcoefficients of thermal expansion for the package materials.
 10. Thecomputer program recited in claim 9, further comprising: identifyinghotspots on the die; determining associated elements on the integratedheat spreader for the hotspots on the die; and modifying the localgeometry of the associative elements on the integrated heat spreader inorder to reduce local thermal resistance.